An electrolyte waste salt containing LiCl and various products is generated during the pyroprocessing of spent nuclear fuel in metal fast reactors. Separating metal impurities from waste salt can purify molten salt, facilitate salt recycling, and reduce the amount of waste salt, achieving waste minimization.

This study aims to investigate the effects of key factors on the application of the cold finger crystallization method used for removal of Sr and Ba from molten LiCl salt.

A homemade cold finger experimental apparatus was applied to the experimental removal of two alkaline earth metals, Sr and Ba, from molten LiCl salt, and Fluent software was employed to simulate the application of cold finger crystallization equipment during dry reprocessing. The effects of crystal growth time, initial crystallization temperature, and initial SrCl₂/BaCl₂ concentrations on the removal ratio of the crystalline salt during the process were analyzed.

The initial temperature of molten salt is a critical factor that influences cold finger separation efficiency. When the initial temperature reaches 660 ℃, the removal efficiency improves. Moreover, when the impurity contents of Sr and Ba in molten salt are lower than 0.55%(w/w), the removal efficiency of the cold finger crystallization method can exceed 80%. Further analysis shows that the removal effects of different parts of molten salt crystals differ. The solvent salt at the top of the molten salt crystal is better, and the removal ratio of the bottom and inner salts is lower. Therefore, the optimal conditions for removing Sr and Ba from LiCl crystalline salt require an initial temperatures of 660~670 ℃, an airflow intensity of 10 L·min^-1, and a growth time of 20 min. Under these optimal conditions, the removal ratio can reach 90%.

The proposed approach is feasible for purifying solvent salts from electrolyte waste molten salt via cold finger crystallization. This study provides a reference for purifying waste salt and reusing molten salt.